Aspects of a Tilting Tower Test

Abstract

Many ancient towers are affected by stability problems. The main part of this thesis is physical modeling of tower. Model test is very appropriate for the stability assessment of tower foundations, which is related to: bearing capacity failure, due to lack of soil strength, instability of equilibrium, due to lack of soil stiffness, and buckling failure of column. The main objective is to measure maximum horizontal displacement at top of a tower before it is permanently failing and to measure the horizontal force to make the tower fall. The results are analyzed with three approaches. One is from pure elastic soil assumption which is not always true. Soil behavior is not elastic. The second approach is stability related to bearing capacity and the third one is buckling failure. The test has been done in the 4mX4mX3m large scale model testing facility at the Geotechnical Division, Norwegian University of Science and Technology, NTNU. A set of electrical instrument are used to perform the test.For analyzing the result it is very important to know about soil behavior. Hokksund sand was used in the sand bin. Three triaxial tests with high confining are done for this thesis. But there are many tests were carried out in the past on Hokksund sand. Results from the past studied carefully and used extensively in this thesis. Another part of this thesis is numerical modeling of tower. Different friction and dilatancy angles were used in the numerical analysis to understand their effect. The results from the model test compared with classical elasticity theory and bearing capacity theory. Some back calculations are also done to compare the results.Conclusions and recommendations for further studies are given at the last of thesis.